After producing Leviathan (1989) for about $30 million, Dino De Laurentiis, albeit uncredited, decided to finance this low budget version of his own bigger budgeted movie. He hired David Coleman to rewrite a 250 pages draft by Colin Wilson. Coleman's work was written in English but it had to be translated into Italian for De Laurentiis and into Spanish for director Juan Piquer Simón who didn't speak English.
At about the 38 minute mark, the submarine is making its way through a tight passage and the character Skeets says "This feels like a golf ball being sucked through a garden hose". This line will seem familiar from another film, Full Metal Jacket, said by R. Lee Ermey who stars in both films.